Field of the Invention
The present invention relates to a charged particle beam writing apparatus and a charged particle beam writing method. More specifically, for example, the present invention relates to a method for correcting a dose of charged particle beam emitted from a writing apparatus.
Description of Related Art
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. For forming a desired circuit pattern on such semiconductor devices, a master or “original” pattern (also referred to as a mask or a reticle) of high accuracy is needed. Thus, the electron beam (EB) writing technique, which intrinsically has excellent resolution, is used for producing such a high-precision master pattern.
FIG. 16 is a conceptual diagram explaining operations of a variable shaping type electron beam writing or “drawing” apparatus. The variable shaping type electron beam writing apparatus operates as described below. A first aperture plate 410 has a quadrangular aperture 411 for shaping an electron beam 330. A second aperture plate 420 has a variable shape aperture 421 for shaping the electron beam 330 having passed through the aperture 411 of the first aperture plate 410 into a desired quadrangular shape. The electron beam 330 emitted from a charged particle source 430 and having passed through the aperture 411 is deflected by a deflector to pass through a part of the variable shape aperture 421 of the second aperture plate 420, and thereby to irradiate a target object or “sample” 340 placed on a stage which continuously moves in one predetermined direction (e.g., the x direction) during writing. In other words, a quadrangular shape that can pass through both the aperture 411 of the first aperture plate 410 and the variable shape aperture 421 of the second aperture plate 420 is used for pattern writing in a writing region of the target object 340 on the stage continuously moving in the x direction. This method for forming a given shape by letting beams pass through both the aperture 411 of the first aperture plate 410 and the variable shape aperture 421 of the second aperture plate 420 is referred to as a variable shaped beam (VSB) system (refer to, e.g., Japanese Patent Application Laid-open (JP-A) No. 2012-069667).
In electron beam writing, dimension change occurs due to a mask process or an unknown mechanism, which is solved by adjusting the amount of dose of an electron beam. In recent years, there is performed setting a dose modulation value which is a value for modulating a dose, which additionally controls a dose amount, for each figure pattern by a user or a correction tool, etc. at the stage before inputting data into a writing apparatus. This technique makes it possible to previously include, in the dose modulation value, a correction amount calculated outside the writing apparatus for correcting a proximity effect and a phenomenon, etc. that affects dimensions in a range smaller than that of the proximity effect. As long as correction is performed for only the proximity effect, etc. previously included in the dose modulation value, what is necessary is just to set a dose, in the writing apparatus, to be in accordance with the dose modulation value. However, in electron beam writing, there is a case where correction calculation is further performed for phenomena, such as a fogging effect and a loading effect, in addition to the proximity effect, (refer to, e.g., Japanese Patent Application Laid-open No. 2012-069667). Conventionally, correction calculation is performed for a proximity effect inside the writing apparatus, and using a result of this calculation, correction calculation is performed for a fogging effect or a loading effect. Therefore, if a correction amount for proximity effect correction is included in the dose modulation value input from the outside of the apparatus, there occurs a problem in that it becomes difficult to perform correction calculation for a fogging effect or a loading effect in the writing apparatus. It may be theoretically possible to also calculate an amount of correction of the fogging effect and the loading effect outside the writing apparatus and input the amount into the apparatus. However, in that case, since pattern data of the same chip needs to be prepared for each global arrangement, the amount of the data to be input into the writing apparatus becomes enormous.